Lexus LS400 (2000 year). Manual — part 31

BE0CW–01

N13319

ON

N06769

–

BE–201

2064

INSPECTION

1.

INSPECT FUEL LID OPENER SWITCH CONTINUITY

(a)

Check that there is continuity between terminals with the
switch ON (Lever pulled).

(b)

Check that there is no continuity between terminals with
the switch OFF (Lever free).

If continuity is not as specified, replace the switch assembly.

2.

INSPECT FUEL LID OPENER SOLENOID OPERATION

(a)

Apply battery positive voltage to the terminals.

(b)

Check that the solenoid operates in the open direction.

If operation is not as specified, replace the solenoid.

The radio wave bands used in radio broadcasting are as follows:

Frequency

Designation

Radio wave

Modulation method

LF: Low frequency MF: Medium Frequency HF: High Frequency VHF: Very High Frequency

Amplitude modulation

Frequency modulation

30 kHz

300 kHz

3 MHz

30 MHz

300 MHz

LF

MF

HF

VHF

AM

FM

BE0CX–03

BE2818

FM (Stereo)

FM (Monaural)

AM

BE2819

Fading

Ionosphere

BE–202

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BODY ELECTRICAL

AUDIO SYSTEM

2065

AUDIO SYSTEM

DESCRIPTION

1.

RADIO WAVE BAND

2.

SERVICE AREA

There are great differences in the size of the service area for AM
and FM monaural. Sometimes FM stereo broadcasts cannot be
received even through AM can be received in very clearly.
Not only does FM stereo have the smallest service area, but it
also picks up static and other types of interference (”noise”)
easily.

3.

RECEPTION PROBLEMS

Besides the problem of static, there are also the problems
called ”fading”, ”multipath” and ”fade out”. These problems are
caused not by electrical noise but by the nature of the radio
waves themselves.

(1)

Fading
Besides electrical interference, AM broadcasts are
also susceptible to other types of interference, es-
pecially at night. This is because AM radio waves
bounce off the ionosphere at night. These radio
waves then interfere with the signals from the same
transmitter that reach the vehicle’s antenna directly.
This type of interference is called ”fading”.

BE2820

Multipath

BE2821

Fade Out

AM

FM

Noise occurs at a specific place.

Strong possibility of foreign noise.

Noise occurs when listening to
faint broadcasting.

Noise occurs only at night.

Noise occurs while driving and
at a specific place.

There is a case that the same program is broadcasted
from each local station and that may be the case you are
listening different station if the program is the same.

Strong possibility of the beat from a distant broadcasting.

Strong possibility of multipath noise and fading noise
caused by the changes of FM waves.

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BODY ELECTRICAL

AUDIO SYSTEM

BE–203

2066

(2)

Multipath
One type of interference caused by the bounce of
radio waves off of obstructions is called ”multipath”.
Multipath occurs when a signal from the broadcast
transmitter antenna bounces off buildings and
mountains and interferes with the signal that is re-
ceived directly.

(3)

Fade Out
Because FM radio waves are of higher frequencies
than AM radio waves, they bounce off buildings,
mountains, and other obstructions. For this reason,
FM signals often seem to gradually disappear or
fade away as the vehicle goes behind a building or
other obstruction. This is called ”fade out”.

4.

NOISE PROBLEMS

(a)

Questionnaire for noise:
It is very important for noise troubleshooting to have good
understanding of the claims from the customers, so that
make the best use of following questionnaire and diag-
nose the problem accurately.

HINT:
In the case that the noise occurrence condition does not meet
any of the above questionnaire, check based on the ”Trouble
Phenomenon”.
Refer to above descriptions for multipath and fading.

N21545

Glass Printed Antenna

Noise

Signal

Radio

Noise

Noise

Noise

Noise

N21546

to Radio

Battery

Noise

Choke Coil

BE–204

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BODY ELECTRICAL

AUDIO SYSTEM

2067

(b)

Matters that require attention when checking:

Noise coming into the radio usually has no harm for
practical use as the noise protection is taken and it
is hardly thinkable for an extremely loud noise to
come in. When extremely loud noise comes into the
radio, check if the grounding is normal where the
antenna is installed.

Check if all the regular noise prevention parts are
properly installed and if there is any installation of
non–authorized parts and non–authorized wiring.

If you leave the radio under out of tune (not tuning),
it is easy to diagnose the phenomenon as noise oc-
curs frequently.

(c)

Antenna and noise:
Electronic signal received by the antenna will reach to the
radio transmitting through the core wire of the coaxial
cable. Any noise wave other than radio wave is mixed into
this core wire, that naturally causes noise in the radio and
poor sound quality. In order to prevent these noises from
mixing into the radio, the core wire inside the coaxial cable
is covered with a mesh wire called shield wire. This shield
wire shelters the noise and transmits it to the ground, thus
preventing noise from mixing in.

If this shield wire has grounding failure, that causes noise.

(d)

Choke coil and noise:
The choke coil is connected in the rear window defogger
circuit. This is connected so to prevent noise from mixing
into the radio by making the noise current included in the
power source of the rear window defogger flow to the
ground.